UGC-NET (NTA) Environmental Sciences, December-2019

Total Questions: 100

71. Beaufort Scale is used to classify which of the following meteorological parameters?

Correct Answer: D. Wind Velocity
Solution:

Beaufort Wind Scale. One of the first scales to estimate wind speeds and the effects was created by Britain's Admiral Sir Francis Beaufort (1774-1857). He developed the scale in 1805 to help sailors estimate the winds via visual observations. The scale starts with 0 and goes to a force of 12.

72. How many years will it take for the population of a country to double, if it grows at the rate of 4 percent per year?

Correct Answer: A.~ 17.3 years

73. Which of the following particulate control devices has the poorest removal efficiency for particles in the sub-micron size range?

Correct Answer: C. Cyclone
Solution:

Cyclone separators provide a method of removing particulate matter from air or other gas streams at low cost and low maintenance. The efficiency of cyclones greatly depends on the size of the particulate, the larger particle being removed at higher efficiency than smaller particles.
Among Electrostatic Precipitator, Fabric Filter, cyclone and Venturi Scrubber, cyclone has the poorest removal efficiency for particles in the sub-micron size range.

74. Which of the following measures of skewness is based on the distance of upper and lower quartiles from the median value in a dataset?

Correct Answer: C. Bowley's Coefficient of Skewness
Solution:

Bowley's Coefficient of Skewness: This method is based on quartiles, i.e., second absolute measure of skewness. The formula for calculating skewness is:
This method is particularly useful in case of open end distributions and where extreme values are present or when class-intervals are unequal. Skewness should be measured by this Bowley's method also when positional measures are called for.
If the value of this coefficient is zero, it is a symmetrical distribution. For positive value, it is a positively skewed distribution and for a negative value it is a negatively skewed distribution. The range of variation under this formula is ± 1. But the main drawback of this measure is that it is based on central 50% of the data and it ignores the remaining 50% of the data i.e., 25% of the data below Q, and 25% of the data above Q3

75. Which one of the following is NOT a constituent of photochemical smog?

Correct Answer: C. Polycyclic Armoatic Hydrocarbons
Solution:

Peroxy acetyl nitrate (PAN) is the most abundant peroxy acyl nitrate and is an important component of photochemical smog in urban areas. PAN is largely responsible for the eye irritation experienced in smog episodes and, because of its phytotoxic nature, can damage agricultural crops. Other members of the peroxy acyl nitrate family include peroxy propyl nitrate, C₂H₅C(O)O₂NO₂, and peroxy benzoyl nitrate, C₆H₅C(O)O₂ NO₂, which are found at levels ranging from a few per cent to 30% of that of PAN. Photolysis of NO₂ is an important source of tropospheric ozone and is responsible for the formation of photochemical smog in polluted air masses.

76. Phytoremediation is an important tool for:

Correct Answer: D. removing toxic chemicals from the polluted ecosystem
Solution:

Phytoremediation is an eco-friendly and advantageous technique for the cleaning of contaminated media. The mechanism involves is absorption of pollutants through roots, accumulation in body tissues, decompose and transforming pollutants to a less harmful forms.

77. Restoration of Doon Valley is an example of best practices of restoration of degraded ecosystem caused by:

Correct Answer: C. limestone quarrying
Solution:

Doon valley and Mussoorie hills (Garhwal Himalayas of Uttarakhand, India) till early eighties faced a serious threat due to heavy limestone quarrying with 105 working mines in this region. After the cessation of mining activity restoration of these sites was undertaken by different agencies. The ecological restoration interventions were initiated in these areas during 1988-1989. Ecology of this region was adversely affected by large scale limestone quarrying.

78. Consider the following statements regarding Chi-Square test:

(a) If X is a random variable following normal distribution with mean u and standard deviation σ, then (X-u/σ)² is a Chi-square variate with 1 degree of freedom
(b) It is an appropriate test for testing the goodness of fit of a model/theory to experimental data
(c) It involves computing the squares of the deviations of observed frequencies from the expected frequencies
Which of the above statements are correct?

Correct Answer: D. (a), (b) and (c)
Solution:

Pearson's chi-squared test is used to assess three types of comparison: goodness of fit, homogeneity, and independence.
• A test of goodness of fit establishes whether an observed frequency distribution differs from a theoretical distribution.
• A test of homogeneity compares the distribution of counts for two or more groups using the same categorical variable (e.g. choice of activity-college, military, employment, travel-of graduates of a high school reported a year after graduation, sorted by graduation year, to see if number of graduates choosing a given activity has changed from class to class, or from decade to decade).
• A test of independence assesses whether observations consisting of measures on two variables, expressed in a contingency table, are independent of each other.

79. 50 mm of rainfall was recorded during 30 min of rain in an area of 2.5 ha. The total volume of water that fell on that area during the rain would be:

Correct Answer: B. 1250 m³
Solution:

50 mm = 50 × 10⁻³
1 hectare = 10000 m²
Volume of water = 5 x 10⁻³ x 2.5 × 10⁴
= 1250 m³.

80. Which among the following radioactive species have a half life of more than 10 years?

(a) ₃₆Kr⁹¹                (b) ₃₈Sr⁹⁰
(c) ₅₅Cs¹³⁷              (d) ₄₀Zr⁹¹
Choose the correct option from those given below:

Correct Answer: B. (b) and (c) only
Solution:

Several radioactive isotopes were released in huge quantities, contaminating many thousands of square kilometers and directly affecting hundreds of thousands of people. The most significant releases were of ¹³¹I,⁹⁰Sr, ¹³⁷Cs, ²³⁹Pu, ²³⁸U, and ²³⁵U. Estimates are that the total amount of radiation released was about 100 million curies.
These radioactive species have a half life of more than 10 years.